stdragon :
"Unfortunately, X399 motherboards are only certified to support up to 128GB"
Why is that a MB has to be "certified" to a *capacity* when what really matters is the CPU, RAM clocking and timings/latency? The only limitations that a MB should have with regards to capacity is the amount of DIMM slots available.
This is not the case. When the capacity gets really high, it has to make sacrifices in other areas, like performance. Getting the many chips on a DIMM to run at a certain frequency is harder than doing it with less.
Also certification reduces headache the manufacturer has to deal with when a customer calls in and say its not compatible, and possible additional modifications the board needs to guarantee compatibility.
Interesting, that would render Intel 3DXPOINT technology irrelevant. That is quite interesting to see that RAM is maybe still the way to go.
Actually 3D XPoint DIMMs will be available in 128GB/256GB/512GB sizes, are nonvolatile, and cost less per GB. Plus, the total capacity of the system is going to be Intel DIMM + DRAM DIMM.
So in case of a dual socket system with 2 DIMMs per channel using Intel DIMMs, the potential capacity is:
DRAM = 256GB x 6 channels x 2 sockets = 3 TB
Intel DIMM = 512GB x 6 channels x 2 sockets = 6GB
Total = 9TB